1. Field of the Invention
The present invention relates to a display device and a television receiver equipped with a diffusion plate facing a display panel such as a liquid crystal panel.
2. Description of the Related Art
A conventional display device such as a television receiver is disclosed in JP-A-2005-276716 (See, for example, pages 4 and 5, and FIG. 1 of this reference). The display device is provided with an illumination apparatus on the rear side of a display panel such as a liquid crystal panel. The illumination apparatus has a light source and a diffusion plate, each supported by a chassis. The diffusion plate is disposed so as to face the display panel, and diffuses light emitted from the light source provided on the rear side so as to direct it to the display panel.
At a light-emitting side of the diffusion plate, there is provided an optical sheet such as a lens sheet or a prism sheet. The diffusion plate and the optical sheet are retained by sandwiching peripheral portions thereof between a metal retainer fitted to the chassis and the chassis. Thus, the diffusion plate and the optical sheet are integrally fitted to the chassis.
When the light source is turned on, the optical sheet stretches due to a rise in temperature; the optical sheet is thus wrinkled with a strong pressing force produced by the metal retainer, causing a portion of a display image to be dark on the display panel. To cope with this, a gap is provided between the metal retainer and the optical sheet, making it possible to retain the optical sheet so as to freely stretch and contract, so as to obtain satisfactory images.
With the aforementioned conventional display device, however, if increased in size, the diffusion plate is warped with a rise in temperature caused by turning on the light source. FIGS. 16A and 16B are perspective views each showing how the diffusion plate is warped. Owing to a rise in temperature, the diffusion plate 10 may be warped to be formed in a cylinder-like shape (FIG. 16A), or in a saddle-like shape (FIG. 16B), so that a central portion thereof protrudes or is recessed toward the display panel.
Being increasingly warped, the diffusion plate comes into contact with the metal retainer so as to cause it to be elastically deformed. As a result, the diffusion plate may be brought into contact with the display panel. Moreover, the optical sheet is sandwiched between the warped diffusion plate and the metal retainer, and the optical sheet that is stretched due to a rise in temperature is thus wrinkled. This disadvantageously makes it impossible to obtain satisfactory display images. By forming the metal retainer with a member having great rigidity, it is possible to prevent warpage of the diffusion plate, but it is impossible to eliminate wrinkling of the optical sheet.